Strain insulator



April 29, 1930'.I

s. SMATTHES STRAIN INSULATOR Filed March 18, 1927 JAMUEL .5. M4 777/55 Patented Apr. 29, 1930 UNITED STATES PATENT Price `SAMUEL S. MATTHES, OF MANSFIELD, OI-IIO, ASSIGNOR TO THE OHIO BRASS COMPAY, v OF MANSFIELD, OHIO, A CORPORATION OF NEW JERSEY STRAIN rNsULA'ron Application. filed March 18, 1927. Serial No. 176,352.

My invention relates to strain type of insulators in which porcelain is preferably used, andA in which the insulator is placed under compression rather than tension.

It is well known that porcelain is a more or less fragile material, and it is advisable when the porcelain is used under strains to 'distributethe strain over as large an area as practical, thereby reducing the strain per unit of area of Contact between the parts.

In the past, sometimes provision has been made to distribute this strain to a limited degree by the use of a thin sheet of lead between the metal parts and the porcelain, andthis is possibly satisfactory under some conditions of insulator design. In other cases practically no provision is made at all for Ldistribution of the strain.

The object of my inventionis to employ a porcelain insulating element of approved-design, and which is considered a standard on the market at the present day, and I have so arranged the parts through which strainis subjected fto the insulator'that'such strain will be quite uniformly distributed.

My invention resides in the new and novel construction, combination and relation ofthe various parts hereinafter `fully described and shown in the accompanying drawing.

Fig. 1 is aview of one faceof my invention comprising two insulating units' and one of which is in section; Y Y

Fig. 2.is alview of another face of the invention. 'shown in Fig. 1 and 'at 90 degrees from that of Fig. 1 about a longitudinal axis. Inpthis vfigure one of the insulating elements is'shownin section. u

Figf` is `afsideview of a shim member 4which'I employ.

VFig/1 is an end View of Fig. 1.

Figj5 `is a top view of Figs. 3 and 4. In the preferredembodiment of my invenf 'tion Ifemploy two insulating members 1 which are provided with transverse passages 2 and 3 `at right angles to each other. The bearing surfaces of these passages is made to a radius, as this type of insulator is a standard, and wasprimarilyintended for use with a flexiblecable,'therefore, the bearing surface is made to conform 'to the radius of a circle. In this type of insulator the porcelain is placed under compression and the insulator has proved to be a very eflicient one, both mechanically and electrically, especially when used with a flexible cable.

In -order to adopt the insulator for use with rigid fittings, I provide a means interposed between through bolts 4 and the curved bearing surface of the insulator for distributing the strain between the bolts 4 and the insulator uniformly over not only the Asurface of the insulator', but the surface of the bolt as far as possible. The entire makeup of the insulator, as shown in Fig. 1, comprises the two insulating members 1, the yoke members 5` and 6 and the link members 7 The yoke members may both be like the member 5, or they may both be like the member 6, the difference being one of choice between an eye and clevis. The yoke and link members are secured in position by meansof the through bolts 4 and 8 respectively. The bolts are held in position by means of the spring cotters 9 or by other vwell known suitable means.

Between the through bolts and the insulator is a shim 10 which is provided with a curvedsurface 11 adapted to conform reasonably close to a curved surface 12 on the insulator.

The radius of the curved surface 11 can be made exactly that of the radius of the curved surface 12., V'Ihe radius ofthe curved surface`11 is preferably made a little largerrthan that of the radius of the curved surface 12, so that under strain the curved surface will change. andy conform to the radius of the porcelain.

The shim 10 is provided with a groove 13 to receive the through bolts 4'or 8, and the bearing surface 14 of the groove 13 is made yslightly concave with respect to the surface of the bolt, so that when the strain is first broughtuponthe shim it will bear at the extreme Apoints 15. This will permit the surface 14 to assume substantially a straight line under strain as the surface 11 to .that of the insulator. Y 1 This construction also prevents the bendconforms bolt, causing the same to bend, but it will be readily appreciated that with the construe tion described, the strain on the bolt is substantially one of shearing, andthe length of the shim is substantially that of the width of the space between the inner faces of the yoke members and also of the link member 7 when the device is assembled.

In Fig. l, it will be noted that the surface 'll of the shim conforms to the surface of the porcelain and the surface 14 of the shim is slightly concave regarding the bolt, and this construction I find gives ideal conditions as it distributes the strain uniformly over the contact surface of the insulator, and places substantially a shearing strain only upon the bolts 4 and 8. This shearing strain will also be accomplished, of course, if the surface 14 of the shim is substantially straight, so that it lnot higher at the center than at the ends.

I prefer to make the shim l() of a yielding material such as a malleable cast iron or forging, copper or of a copper base casting. Of course, aluminum may be used, and likewise lead, Zinc or tin, ybut the lead Linder the circumstances, I-nd, to be soft where the strain is substantial, and zinc or tin do not seem to have any advantage over a bronze or brass casting.

It will be appreciated that in place of the link 7, the member 5 or 6 may be substituted, thereby making a single insulator strain device instead of a double. y Y

The construction described, especially that of the shim, provides means of getting a maximum strength out of the device, in that the strain is quite uniformly distributed over the bearing surface of the insulator, and the 'strain upon tne bolt is one ofshear rather than bend.

The shims l0 are first placed in position before the bolts are positioned, as usually the transverse passages 2 are not large enough to permit the insertion of the shims l0 after the throng.' bolts have been inserted.

p My invention also has the advantage that the parts can be shipped from the factory in an unassembled condition and assembled in the field into either the single or double form as desired, and without the use of any tools whatsoever, other than possibly a screw driver to open up the ends of the spring cotter .(5 slightly. i

There will be modifications, of course, toV

my invention, which will suggest themselves to those skilled in the art, therefore, I doY not wish to be limited other than by my claims.

I claim: Y l. An insulator comprising an insulating element having transverse passages spaced apart and having axes at right angles to each other and also having curved bearing surfaces, bolts passing through the passages and fittings secured to the bolts and so disposed as to subject the insulator to compression and a yielding member interposed between each bolt and the insulator to distribute the strain over the bearing surface of the insulator and having a surface to conform to the bearing surface on the insulator and a surface adjacent the bolt and slightly concave thereto.

2. An insulator comprising an insulating member, and metal fittings secured thereto by transversely disposed bolts whose axes are at right angles to each other, shims interposed between the bolts and the insulating member and of such length as to extend beyond the sides of the insulating member, each shim having a surface to conform to the surface of the insulator which it engages and means at the endsof the shims to engage the bolts.

An insulator comprising aninsulating member, metallic fittings secured thereto by transversely disposed bolts Whose axes are at ri ght angles to each other, shims disposed between the bolts and the insulating member and each of such length as to extend beyond the sides of the insulating member, each shim also having a. surface to conform to the bearing surface of the insulator and an oppositely disposed groove having a surface arranged to initially engage its bolt at the ends only of the shim to receive the bolt.

4. An insulator comprising a pair of insulating members spaced apart and each having two transversely disposed passages whose axes are at right angles, yoke shaped fittings secured to each insulating member by means of a bolt extending through that passage which'is nearest the other insulating member when fully assembled, a pair of link fittings spaced apart and secured to opposite ysides of the insulatingy members by bolts extending through ythe passages which are farthest from the other insulating Vmember and thereby interlinking the fittings and bringing a compressive strain upon the insulating members when in use, a yieldable shim interposed between each. bolt and the corresponding bearin g surface on the. insulating member and having a surface adapted to be shaped to the bearing surface on the insulatingv member when under stress and having a groove to receive the bolt, the surface of the groove arranged to initially engage the respective bolts only at points adjacent to the fittings.

5. The combination of .an insulator having a bearing surface, a shim formed of a yieldable metal having asurface to rest against the said bearing surface and to conform to the bearingsurface under strain, a groove in the shim, a bolt or pin resting in the groove, the surface of the groove adapted to initially engage the bolt or pin only at' the outer ends of the groove and supporting means secured to the bolt or pin.

6. An insulator tting comprising a yoke shaped member and a substantially straight and transversely positioned bolt connecting the free ends of the yoke and an elongated shim of deformable metal engaging the bolt bet-Ween the ends of the yoke member, the shim having a groove in which the bolt is positioned, the surface of the groove being coneavo-eoncave to engage the bolt initially at the ends of the shim and a groove transversely disposed to the first groove and having a concavo-oonvex bearing surface and securing means on the yoke at the closed end thereof.

In testimony whereof I ax my signature.

SAMUEL S. MATTHES. 

